<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<style>
    /**div中第一个字母**/
    div::first-letter{
        font-size: 40px;
        color: red;
    }
    /**div中第一行**/
    div::first-line {
        color: yellow;
    }
    /**div中选中文字**/
    div::selection{
        background-color: orange;
    }
    /**input中提示**/
    input::placeholder{
        color: green;
    }
    /**p中内容前添加￥**/
    p::before{
        content: "￥";
    }
    /**p中内容后添加.00**/
    p::after{
        content: ".00";
    }


</style>
<body>
    <div> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbccccccccccccccccccccccccccccc</div>
    <input type="text" placeholder="输入内容">
    <p>600</p>
    <p>255</p>
    <p>100</p>
</body>
</html>
